Hardmask films are commonly used as sacrificial layers during lithographic patterning, e.g., during trench and/or via formation in a Damascene process. In Damascene processing, hardmask film is typically deposited onto a layer of dielectric that needs to be patterned. A layer of photoresist is deposited over the hardmask film (with an optional antireflective layer deposited between the hardmask and the photoresist), and the photoresist is patterned as desired. The lasers are typically used for alignment of the pattern with the underlying structures, and, hence, the hardmasks should be substantially transparent at the wavelengths used for alignment. After the photoresist is developed, the exposed hardmask film below the pattern is removed, and the exposed dielectric is etched such that recessed features of required dimensions are formed. The remaining hardmask serves to protect those portions of dielectric that need to be preserved during the etching process. Therefore, the hardmask material should have a good etch selectivity relative to the dielectric. Reactive ion etching (RIE) which uses halogen-based plasma chemistry is typically employed for dielectric etching.
The etched recessed features are then filled with a conductive material, such as copper, forming the conductive paths of an integrated circuit. Typically, after the recessed features are filled, the hardmask material is completely removed from the partially fabricated semiconductor substrate.
Titanium nitride deposited by physical vapor deposition (PVD) is currently commonly used as a hardmask material for this application. The use of silicon carbide as a hardmask material has also been reported in U.S. Pat. No. 6,455,409 and U.S. Pat. No. 6,506,692.